Pharmacotherapeutic group: Calcium homeostasis, parathyroid hormones and analogues, ATC code: H05AA04
Mechanism of action
Abaloparatide is a 34 amino acid peptide that shares 41% homology to parathyroid hormone [PTH(1-34)] and 76% homology to parathyroid hormone related peptide [PTHrP(1-34)], and is an activator of the PTH1 receptor signalling pathway. Abaloparatide stimulates new bone formation on trabecular and cortical bone surfaces by stimulation of osteoblastic activity.
Abaloparatide causes transient and limited increases in bone resorption and increases bone density.
Clinical efficacy and safety
The efficacy and safety of once daily abaloparatide was evaluated in a randomised, multicentre, double-blind, placebo- and open-label active comparator-controlled (teriparatide) clinical study (ACTIVE study) for 18 months of treatment with 1 month follow-up in 2 070 postmenopausal women aged 50 to 86 years (mean age of 69; 15% were <65 years of age, 65% were 65 to ˂75 years of age, and 20% were ≥75 years of age) who were enrolled and randomised to receive abaloparatide 80 micrograms (N=696), placebo (N=688), or 20 micrograms teriparatide (N=686). Approximately 76% of patients were Caucasian, 19% were Asian, and 4% were Black. Of the total study population, 28% were Hispanic. Women took daily supplemental calcium (500 to 1 000 mg) and vitamin D (400 to 800 IU) per day. The primary endpoint in ACTIVE was the incidence of new vertebral fractures in abaloparatide-treated patients versus placebo.
At baseline, the mean T-scores were -2.9 at the lumbar spine, -2.2 at the femoral neck, and -1.9 at the total hip. At baseline, 42% of patients had no prior fracture, 23% of patients had at least one prevalent vertebral fracture, and 43% had at least one prior non-vertebral fracture.
Effect on new vertebral fractures
In the ACTIVE study at 18 months, abaloparatide and teriparatide significantly reduced the absolute risk of new vertebral fractures versus placebo in postmenopausal patients with osteoporosis (p<0.0001; see Table 2).
Table 2 – ACTIVE Trial: the effect* of abaloparatide on the risk of new vertebral fracture at 18 months
| Parameter | PBO (N=600) | ABL (N=583) | TER (N=600) |
| Number of women with vertebral fracture, n (%) | 25 (4.2) | 3 (0.5) | 4 (0.7) |
| Absolute risk difference vs placebo† (%) (95% CI) | n/a | 3.7 (2.0, 5.6) | 3.5 (1.8, 5.5) |
*Based on Modified Intent to Treat Population (patients with baseline and post-baseline spine radiographs).
† Absolute risk difference was calculated as (PBO – ABL) and (PBO – TER).
PBO=placebo, ABL=abaloparatide, TER=teriparatide, CI=confidence interval
Effect on non-vertebral fractures
In the ACTIVE study at 19 months, the incidence of non-vertebral fractures was similar between the abaloparatide (2.7%) and teriparatide (2.0%) groups, and not statistically different compared to placebo (3.6%) (see Table 3).
Table 3 – ACTIVE Trial: time-to-event of non-vertebral fracture at 19 months
| Parameter | PBO (N=688) | ABL (N=696) | TER (N=686) |
| K-M estimated event rate (%) (95% CI) | 3.6 (2.3, 5.4) | 2.7 (1.6, 4.4) | 2.0 (1.1, 3.4) |
| Number of patients with event n (%) | 21 (3.1) | 15 (2.2) | 12 (1.7) |
| Absolute risk difference vs placebo* (%) (95% CI) | n/a | 0.9 (-1.1, 2.9) | 1.6 (-0.3, 3.5) |
*Absolute risk difference was calculated as (PBO – ABL) and (PBO – TER).
PBO=placebo, ABL= abaloparatide, TER=teriparatide, K-M=Kaplan Meier, CI=confidence interval
Effect on bone mineral density (BMD)
In the ACTIVE study, abaloparatide significantly increased BMD at all anatomical sites measured, versus placebo at 6, 12 and 18 months. The mean percent change in BMD at 18 months was 9.1% vs 0.5% at the lumbar spine, 3.3% vs 0% at the total hip, and 2.7% vs -0.4% at the femoral neck for abaloparatide versus placebo groups, respectively (all p<0.0001). At the ultra-distal radius, the mean percent change in BMD at 18 months was 1.2% vs -1.0% for abaloparatide versus placebo groups.
Abaloparatide demonstrated consistent increases in BMD measurements regardless of age, years since menopause, race, geographic region, presence or absence of prior fracture (vertebral, non-vertebral), severity of disease, and BMD at baseline.
Bone turnover markers
In postmenopausal women with osteoporosis, the bone anabolic marker (s-PINP) showed a 90% increase above baseline at 1 month, and this effect was sustained throughout the abaloparatide treatment period. The bone resorption marker (s-CTX) showed no increase at 1 month, and a transient 22% increase above baseline at 3 months that returned to baseline at the end of treatment.
Post treatment management
Extension study
Upon completion of the ACTIVE trial, 963 patients, enrolled in the ACTIVExtend trial, an open-label extension study, where all patients received up to 24 months of treatment with 70 mg alendronate (ALN) weekly and calcium and vitamin D supplements. This included 494 patients who had previously received placebo and 469 patients who had previously received abaloparatide. Patients who received teriparatide during the ACTIVE trial were not eligible to participate in the ACTIVExtend trial. Results for vertebral fracture risk reduction at 43 months since randomisation are presented in Table 4.
Effect on new vertebral fractures – Extension study
In the ACTIVExtend study at 43 months, abaloparatide/ALN significantly reduced the absolute risk of new vertebral fractures vs placebo/ALN (p<0.0001; see Table 4). Teriparatide followed by alendronate has not been studied.
Table 4 – ACTIVExtend trial: the effect* of abaloparatide/ALN on the risk of new vertebral fracture at 43 months†
| Parameter | PBO/ALN (N=489) | ABL/ALN (N=457) |
| Number of women with vertebral fracture, n (%) | 26 (5.3) | 4 (0.9) |
| Absolute risk difference vs placebo/ALN‡ (%) (95% CI) | n/a | 4.4 (2.3, 6.9) |
*Based on Modified Intent to Treat Population (patients with baseline and post-baseline spine radiographs).
† Alendronate started at 19 months
‡ Absolute risk difference was calculated as (PBO/ALN – ABL/ALN).
PBO=placebo, ABL=abaloparatide, ALN=alendronate, CI=confidence interval
Effect on non-vertebral fractures – Extension study
In the ACTIVExtend study at 43 months, abaloparatide/ALN numerically reduced the risk of non-vertebral fractures versus placebo/ALN. The incidence of non-vertebral fractures with abaloparatide/ALN (4.2%) was not statistically different compared to placebo (6.7%) (see Table 5).
Table 5 – ACTIVExtend trial: time-to-event of non-vertebral fracture at 43 months*
| Parameter | PBO/ALN (N=494) | ABL/ALN (N=469) |
| K-M estimated event rate (%) (95% CI) | 6.7 (4.8, 9.3) | 4.2 (2.7, 6.4) |
| Number of patients with event n (%) | 32 (6.5) | 19 (4.1) |
| Absolute risk difference vs placebo/ALN† (%) (95% CI) | n/a | 2.5 (-0.4, 5.4) |
*Alendronate started at 19 months
† Absolute risk difference was calculated as (PBO/ALN – ABL/ALN).
PBO=placebo, ABL=abaloparatide, ALN=alendronate, K-M=Kaplan Meier, CI=confidence interval
Effect on bone mineral density (BMD) – Extension study
The mean percent change in BMD through 43 months was 14.7% vs 6.8% at the lumbar spine, 6.3% vs 2.9% at the total hip, 5.0% vs 1.6% at the femoral neck, and 1.1% vs 1.1% at the ultra-distal radius for abaloparatide/ALN versus placebo/ALN groups, respectively.
Paediatric population
The European Medicines Agency has waived the obligation to submit the results of studies with abaloparatide in all subsets of the paediatric population in the treatment of osteoporosis (see section 4.2 for information on paediatric use).